The largest gathering of spaceflight industry stars of the year will convene in Colorado this week for the 29th annual National Space Symposium.

While the convention, which runs from will include leaders from the private space industry, the U.S. military, and international space agencies, a notable segment of its usual attendance will be missing: NASA employees.

The U.S. space agency has expressly forbidden NASA employees from attending the conference on the agency's dime, citing funding concerns under the federal budget sequester. Prominent NASA officials, including the agency's administrator Charles Bolden, who were scheduled to speak at this year's conference have had to bow out.

"We know a lot of people from NASA are really disappointed; they were planning a pretty good presence,"said Janet Stevens, vice president of marketing and communications for the Space Foundation, which sponsors the National Space Symposium. The move sparked a vociferous protest from many in the space industry. [Now Boarding: The Top 10 Private Spaceships]

"We've heard a lot of people say they didn’t think it was the right way to go," Stevens told SPACE.com. "But a lot of people understand what they're up against and we understand that they are trying to make a statement."

Despite NASA's absence, roughly the same number of people — about 9,000 — are expected to attend this year's National Space Symposium as last year's. The conference is held every year at the Broadmoor Hotel in Colorado Springs.

"We do have a much higher number of local Air Force folks attending," Stevens said, pointing out that the U.S. Air Force Space Command is headquartered in Colorado Springs. "The other primarily reason that's helped stabilize us is that our international and commercial involvement keeps growing."

The convention will feature panels on the biggest space issues of the day, such as using satellites for responding to disasters on Earth, the push toward reusable rockets, and long-term sustainability of space activities.

Notable speakers include George Nield, associate administrator for commercial space transportation at the Federal Aviation Administration, Jean-Jacques Dordain, director general of the European Space Agency, and Yasushi Horikawa, chairman of the United Nations Committee on the Peaceful Uses of Outer Space. Officials from commercial space leaders such as SpaceX, Boeing, XCOR Aerospace, Sierra Nevada Space Systems and others, will also speak.

Actress Sigourney Weaver, star of the "Alien" films among others, will be the featured speaker at the Space Technology Hall of Fame gala. "She's got a lot of interests that coincide with ours, supporting education, supporting the environment," Stevens said. "And a part of her history as an actor is playing some pretty iconic space roles."

Visit SPACE.com this week for coverage from the 29th annual National Space Symposium.